One of the problems faced when testing circuits is to know the power level in certain points.... I already did an uncalibrated simple power meter (see: http://speakyssb.blogspot.com/2009/05/attenuator-rf-probe-and-some-matematics.html ) but for very low level measurement I needed something else, so, built also an uncalibrated (yet) power meter based on the AD8307 chip. It's a mix from the datasheet and from the circuit in EMRFD (Experimental Methods for RF Design), the AD8307 part of the diagram is from datasheet and the opamp parts is from EMRFD (placed an 68K resistor in series with my 100uA meter in the original shcematics is an 6K8 for 1mA meter)
Don't have my exact shcematic since I allready closed the box but you can see some similar designs here:
http://vrtp.ru/screenshots/571_2.gif
and here:
http://ok1fmf.net/old/wob70/logzes.html
The front panel: meter, output for a DVM and on/off switch (without button for now)
Inside, se on the back, the rf blindage for the AD8307 chip and the professional batery holder.... the box was from an homebrew swr and I didn't removed all the parts.
p.s.
here's the LM358 part of the schematic, sory for the lousy photo.
No comments:
Post a Comment